Generalizing conditional compilation logic for systems with native utf8 locale.

This change was needed for Chromecast, while avoiding adding yet another
preprocessor condition.

BUG=438331

Review URL: https://codereview.chromium.org/790903003

Cr-Commit-Position: refs/heads/master@{#308109}

base/BUILD.gn

@@ -773,6 +773,12 @@ component("base") {
     "//third_party/modp_b64",
   ]
 
+  # Allow more direct string conversions on platforms with native utf8
+  # strings
+  if (is_mac || is_ios || is_chromeos) {
+    defines += [ "SYSTEM_NATIVE_UTF8" ]
+  }
+
   if (is_android) {
     sources += [
       "memory/discardable_memory_ashmem_allocator.cc",

base/base.gypi

@@ -981,6 +981,11 @@
           ['OS == "win" and >(nacl_untrusted_build)==1', {
               'sources/': [ ['exclude', '\\.h$'] ],
           }],
+          # Enable more direct string conversions on platforms with native utf8
+          # strings
+          ['OS=="mac" or OS=="ios" or <(chromeos)==1 or <(chromecast)==1', {
+            'defines': ['SYSTEM_NATIVE_UTF8'],
+          }],
         ],
       }],
       ['base_i18n_target==1', {

base/files/file_path.cc

@@ -593,7 +593,7 @@ std::string FilePath::MaybeAsASCII() const {
 }
 
 std::string FilePath::AsUTF8Unsafe() const {
-#if defined(OS_MACOSX) || defined(OS_CHROMEOS)
+#if defined(SYSTEM_NATIVE_UTF8)
   return value();
 #else
   return WideToUTF8(SysNativeMBToWide(value()));
@@ -601,7 +601,7 @@ std::string FilePath::AsUTF8Unsafe() const {
 }
 
 string16 FilePath::AsUTF16Unsafe() const {
-#if defined(OS_MACOSX) || defined(OS_CHROMEOS)
+#if defined(SYSTEM_NATIVE_UTF8)
   return UTF8ToUTF16(value());
 #else
   return WideToUTF16(SysNativeMBToWide(value()));
@@ -610,7 +610,7 @@ string16 FilePath::AsUTF16Unsafe() const {
 
 // static
 FilePath FilePath::FromUTF8Unsafe(const std::string& utf8) {
-#if defined(OS_MACOSX) || defined(OS_CHROMEOS)
+#if defined(SYSTEM_NATIVE_UTF8)
   return FilePath(utf8);
 #else
   return FilePath(SysWideToNativeMB(UTF8ToWide(utf8)));
@@ -619,7 +619,7 @@ FilePath FilePath::FromUTF8Unsafe(const std::string& utf8) {
 
 // static
 FilePath FilePath::FromUTF16Unsafe(const string16& utf16) {
-#if defined(OS_MACOSX) || defined(OS_CHROMEOS)
+#if defined(SYSTEM_NATIVE_UTF8)
   return FilePath(UTF16ToUTF8(utf16));
 #else
   return FilePath(SysWideToNativeMB(UTF16ToWide(utf16)));

base/strings/sys_string_conversions_posix.cc

@@ -24,11 +24,10 @@ std::wstring SysUTF8ToWide(const StringPiece& utf8) {
   return out;
 }
 
-#if defined(OS_CHROMEOS) || defined(OS_ANDROID)
+#if defined(SYSTEM_NATIVE_UTF8) || defined(OS_ANDROID)
 // TODO(port): Consider reverting the OS_ANDROID when we have wcrtomb()
 // support and a better understanding of what calls these routines.
 
-// ChromeOS always runs in UTF-8 locale.
 std::string SysWideToNativeMB(const std::wstring& wide) {
   return WideToUTF8(wide);
 }

net/base/filename_util_unittest.cc

@@ -48,6 +48,25 @@ base::FilePath WStringAsFilePath(const std::wstring& str) {
 #endif
 }
 
+std::string GetLocaleWarningString() {
+#if defined(OS_POSIX) && !defined(OS_ANDROID)
+  // The generate filename tests can fail on certain OS_POSIX platforms when
+  // LC_CTYPE is not "utf8" or "utf-8" because some of the string conversions
+  // fail.
+  // This warning text is appended to any test failures to save people time if
+  // this happens to be the cause of failure :)
+  // Note: some platforms (MACOSX, Chromecast) don't have this problem:
+  // setlocale returns "c" but it functions as utf8.  And Android doesn't
+  // have setlocale at all.
+  std::string locale = setlocale(LC_CTYPE, NULL);
+  return " this test may have failed because the current LC_CTYPE locale is "
+         "not utf8 (currently set to " +
+         locale + ")";
+#else
+  return "";
+#endif
+}
+
 void RunGenerateFileNameTestCase(const GenerateFilenameCase* test_case) {
   std::string default_filename(base::WideToUTF8(test_case->default_filename));
   base::FilePath file_path = GenerateFileName(
@@ -55,7 +74,8 @@ void RunGenerateFileNameTestCase(const GenerateFilenameCase* test_case) {
       test_case->referrer_charset, test_case->suggested_filename,
       test_case->mime_type, default_filename);
   EXPECT_EQ(test_case->expected_filename, FilePathAsWString(file_path))
-      << "test case at line number: " << test_case->lineno;
+      << "test case at line number: " << test_case->lineno << "; "
+      << GetLocaleWarningString();
 }
 
 }  // namespace
@@ -418,18 +438,6 @@ TEST(FilenameUtilTest, GenerateSafeFileName) {
 }
 
 TEST(FilenameUtilTest, GenerateFileName) {
-#if defined(OS_POSIX) && !defined(OS_MACOSX) && !defined(OS_ANDROID)
-  // This test doesn't run when the locale is not UTF-8 because some of the
-  // string conversions fail. This is OK (we have the default value) but they
-  // don't match our expectations.
-  std::string locale = setlocale(LC_CTYPE, NULL);
-  base::StringToLowerASCII(&locale);
-  EXPECT_TRUE(locale.find("utf-8") != std::string::npos ||
-              locale.find("utf8") != std::string::npos)
-      << "Your locale (" << locale << ") must be set to UTF-8 "
-      << "for this test to pass!";
-#endif
-
   // Tests whether the correct filename is selected from the the given
   // parameters and that Content-Disposition headers are properly
   // handled including failovers when the header is malformed.